This invention relates generally to apparatus for assisting the lowering of an object into a well and more particularly, but not by way of limitation, to apparatus for preventing a logging tool from becoming stuck on a ledge of an uncased well bore.
An uncased well bore often has identations in the wall defining the bore. These indentations have ledges upon which an elongated logging tool being lowered into the well can become lodged or stuck. It has been the practice that when a tool becomes stuck on such a ledge, the tool be moved up and down (called "yo-yoing" the tool) until the tool is dislodged from the ledge. This "yo-yoing" is often time-consuming because it can take several up-and-down repetitions to dislodge the tool, and it is sometimes totally ineffectual. "Yo-yoing" may even damage the tool if it causes the tool to be banged into the ledge too often or too hard.
To enhance the effectiveness of the "yo-yoing" procedure or to preclude the necessity of "yo-yoing", there is the need for a roller mechanism which can be connected to a tool which is to be lowered into a well. Although there are presently disclosed downhole tool devices which have wheels, these wheels generally extend laterally from the tool so that they can ride along the interior surface of the casing or the surface of the wall defining the uncased well bore. One apparatus having a wheel mechanism extending directly beneath a tool as it is lowered into a well is disclosed in my previously issued patent, U.S. Pat. No. 4,474,235. The apparatus disclosed in this previously issued patent has been in public use for more than one year.
Although the apparatus disclosed in my aforementioned patent satisfies the basic need for a device to enhance or preclude "yo-yoing," I have improved my original concept to enhance its operability.